Question

What is the issue GGavJID ?
Some more details, screenshots, etc., etc., would help us diagnose the problem and supply a solution.

You have come to the right place and the doctor will see you now. What is wrong with your keyframe? Do you feel a curve out of place? Have you been taking your daily dose of Blender?

Dangs, that is a weird one. You delete it and yet it happens again. Can you make that file available please? Upload it and paste the link so we can download it and troubleshoot it on our own.

Hi Gavriel, that is the cyclic modifier doing its thing.

It looks like the other foot loops correctly because you have keyframes from f01-f25

But then on that foot you first show, you only have keyframes from f01-f21.
Therefore you are getting a jump when it loops.

Just copy the start frame over to f25 and it will loop properly.

Hope that makes sense.